Some medical devices are used to deliver electrical stimulation therapy to patients to treat a variety of symptoms or conditions, such as chronic pain, tremor, Parkinson's disease, epilepsy, gastroparesis, urinary or fecal incontinence, and sexual dysfunction. The electrical stimulation is generally delivered to selected target tissues or locations in a patient's body, such as the brain, the spinal cord, pelvic nerves, or peripheral nerves. Hence, stimulation is used in different therapeutic applications, such as spinal cord stimulation (SCS), deep brain stimulation (DBS), gastric stimulation, pelvic stimulation, or peripheral nerve stimulation. Medical devices have also been used to deliver electrical stimulation to the heart, e.g., for cardiac pacing, and muscles, e.g., for functional electrical stimulation (FES) to promote muscle movement or prevent muscle atrophy.